Production of barium hydroxide monohydrate

ABSTRACT

Discrete particles of commercial barium hydroxide monohydrate can be prevented from bonding together into hard, rock-like agglomerates by passing an inert sweep gas over the barium hydroxide monohydrate particles while maintaining them at elevated temperatures in a heating zone to remove substantially all residual water in excess of the stoichiometric amount required to form barium hydroxide monohydrate; the Ba(OH)2 . H20 assay of the resulting monohydrate product is thereby increased and higher hydrates of barium hydroxide are eliminated.

United States Patent Benning [451 May 9,1972

[541 PRODUCTION OF BARIUM HYDROXIDE MONOHYDRATE [63] Continuation ofSer. No. 670,793, Sept. 26, 1967,

abandoned.

[52] U.S. Cl ..23/186, 23/187 [51] Int. Cl. ..C01f 11/02 [58] Field ofSearch ..'..23/186, 187

[56] References Cited UNITED STATES PATENTS 3,082,066 3/1963 Benning..23/186 3,449,075 6/1969 Goldstein et al ..23/l86 FOREIGN PATENTS ORAPPLICATIONS 1,000,301 8/[965 Great Britain ..23/186 OTHER PUBLICATIONSChemical Abstracts 5522435 li Nov. 27, 1961 Primary E.\'aminerOscar R.Vertiz Assistant E.\'aminerG. Alvaro AttorneyEugene G. Seema, Franklanno and Milton Zucker [57] ABSTRACT Discrete particles of commercialbarium hydroxide monohydrate can be prevented from bonding together intohard, rock-like agglomerates by passing an inert sweep gas over thebarium hydroxide monohydrate particles while maintaining them atelevated temperatures in a heating zone to remove substantially allresidual water in excess of the stoichiometric amount required to formbarium hydroxide monohydrate; the Ba(OI-l) H 0 assay of the resultingmonohydrate product is thereby increased and higher hydrates of bariumhydroxide are eliminated.

4 Claims, No Drawings PRODUCTION OF BARIUM HYDROXIDE MONOHYDRATE Thisapplication is a continuation of Ser. No. 670,793 filed Sept. 26, 1967,now abandoned.

BACKGROUND OF THE INVENTION 1 Field of the Invention The inventionrelates to a process for producing barium hydroxide monohydrate which isfree-flowing and which is substantially free of higher hydrates ofbarium hydroxide.

2. Description of the Prior Art Barium hydroxide monohydrate is usefulfor producing additives in oil lubricants used in internal combustionengines. This material is reacted with various organic acids, e.g.,alkyl benzene sulfonates, to form these additives. As a result of thedispersing properties of the organic additives, better lubrication bythe oil is obtained, and the accumulation of hard residues on theinternal walls of the engine is prevented.

At the present time, barium hydroxide monohydrate is employedextensively, compared with other hydrates of barium hydroxide for theabove purposes. This is due, in part, to the high proportion by weightof barium hydroxide in barium hydroxide monohydrate compared with morehighly hydrated forms of barium hydroxide. Another reason is that aparticularly desirable barium hydroxide monohydrate product can beproduced by the process described in U.S. Pat. No. 3,082,066 issued Mar.19, 1963 in the names of Bennie Leroy Benning, et al. This bariumhydroxide monohydrate is desirable because it has a low degree ofreactivity, wherein the activity is a measure of the exothermic reactionof the monohydrate with water. The exact reactivity rate and the methodof determining this rate are set forth in the above-cited patent. Inessence, this desirable barium hydroxide monohydrate product is producedby evaporating a thin film of a 50-66 percent barium hydroxide solutionon a heated surface (225 F. to about 275 F.) whereby rapid removal ofwater is obtained to yield dried flakes of barium hydroxide monohydrate.

One difficulty that has been experienced in using the above bariumhydroxide monohydrate is the tendency of these particles to bondtogether into hard, rock-like agglomerates when these particles remainstanding either in storage or in shipping containers over prolongedperiods. The bonding does not take place when the flakes are firstplaced in bins. It results when the flakes are pressed together, as inpackaging and storage, and allowed to remain for a few weeks. This is aparticularly aggravating phenomenon, since the barium hydroxidemonohydrate flakes are free-flowing and easily handled when shipped intheir containers from the plant, but by the time they arrive at theirdestination, and are unloaded several weeks later, the particles havebonded together into either rock-like agglomerates or into a solidagglomerated mass which is difficult to remove from the containers.Heretofore, the reason for this agglomeration of barium hydroxidemonohydrate particles has not been known, and various measures taken tooffset this agglomeration, e.g., addition of flow promoters, have notproved fruitful.

OBJECTS OF THE INVENTION It is an object of the present invention toproduce discrete particles of barium hydroxide monohydrate which remainfree-flowing after storage and/or shipment.

It is a further object of the present invention to produce a bariumhydroxide monohydrate productin the form of freeflowing, discreteparticles having essentially no higher hydrate forms present.

It is another object of the present invention to produce a free-flowingbarium hydroxide monohydrate which has a desirably low reactivity indexsuitable for use in forming oil additives.

These and other objects will be apparent from the following description.

SUMMARY OF THE INVENTION We have now found that free-flowing, discreteparticles of barium hydroxide monohydrate can be produced which remainfree-flowing without agglomerating into rock-like masses on prolongedstorage or standing by passing barium hydroxide monohydrate particlesinto a heated zone, heating the particles to a temperature of from about100 to 140 C., and passing an inert, sweep gas over the heated particlesto remove residual water in excess of the stoichiometric amount requiredto maintain the monohydrate form of barium hydroxide; the Ba(OH) H Oassay of the resulting product is thereby increased (preferably to atleast about 99 percent by weight of Ba(OI-I) H 0) and higher hydrates ofbarium hydroxide are eliminated.

DESCRIPTION OF THE INVENTION AND THE PREFERRED EMBODIMENTS In carryingout the present invention, a conventional barium hydroxide monohydrateis first formed. One convenient method of producing a desirable bariumhydroxide monohydrate having a low reactivity rate, as described in U.S.Pat. No. 3,082,066 described above, is to heat a solution of bariumhydroxide containing from about 50-66 percent bariurn hydroxide to atemperature of -1 10 C. This solution is then fed to a disperser whichuniformly distributes the solution of barium hydroxide in a thin liquidlayer on a smooth, heated surface wherein the layer of solution is nothicker than about 0.025 inches. The heated surface may be any meansthat can rapidly heat the thin film of barium hydroxide solution anddrive off excess water. The heated surface normally is maintained at atemperature of about 107 to 135 C. (225 to 275 F.). When the water hasbeen driven off, the resultant barium hydroxide monohydrate (assay about97.5% Ba(Ol-I) H O) is removed from the heated surface as small flakesand generally has a particle distribution as follows:

7 to 11% +8 mesh 75 to 78% 8 +200 mesh.

In accordance with the present invention, the barium hydroxidemonohydrate thus formed is placed in a heated zone and heated to atemperature of--140 C. An inert, sweep gas is then passed over theparticles of barium hydroxide monohydrate in the heated zone. The sweepgas, may for convenience sake, be air, nitrogen, helium or any gas whichis nonreactive with barium hydroxide monohydrate. Where air is utilized,the CO content of the air must be removed or kept extremely low, sinceCO will react with the barium hydroxide monohydrate to form bariumcarbonate.

The function of the sweep gas is to remove residual water from thebarium hydroxide monohydrate product in excess of the stoichiometricamount required to produce barium hydroxide monohydrate. By thistechnique, higher hydrates of barium hydroxide which are present in theproduct are converted to barium hydroxide monohydrate with the releaseof the excess water vapor. This treatment is continued until the excesswater has been removed. Periods of about I to 30 minutes have been foundeffective in removing the water. As a result of this treatment, theresulting product normally has an assay of at least about 99 percent byweight Ba(OH) H O. The remaining impurities which constitute less .than1 percent of the barium hydroxide monohydrate product are made up oftrace amounts of barium carbonate, barium sulfate, and other suchcompounds.

In carrying out the above process the heating zone may be either arotary kiln or a fluidized bed. In the case of a rotary kiln, the inertgas stream may be passed either cocurrently or countercurrently throughthe kiln, while the particles of barium hydroxide monohydrate aretumbled within the kiln. The rotary kiln may be heated by electricalresistance heating means or by burning gas and contacting the kiln withthe hot combustion products. However, in the latter case, the combustionproducts must be kept out of contact with the sweep gas stream and thebarium hydroxide monohydrate being treated within the kiln. This can bedone by passing the hot combustion products around the outside of thekiln and obtaining indirect heat exchange through the walls of the kiln.Other methods of heating such as contacting the outside of the kiln withsteam tubes or a heat transfer medium, e.g., Dowtherm, can also beemployed.

In the case of a fluidized bed, an upflowing gas stream is used tosuspend the particles in a container in a fluidized state. Thefluidizing gas may act as the sweep gas, provided this gas isnonreactive with the barium hydroxide monohydrate being treated. The bedmay be heated by using electrical resistance heating means placed withinor about the bed or by passing heated gases, steam or a heat transferliquid, e.g., Dowtherm, through jackets located around the outside wallof the fluidized reactor. Heating can also be achieved by heating thefluidizing gas which flows upwardly through the bed. In this lattercase, the gas must not contain carbon dioxide or reaction products fromany burning gases, since these will contaminate the product.

The rate of flow of the sweep gas is not critical, but it should besufficient to remove the excess moisture within a practical, commercialoperating time. The exact flow rate will depend also on the amount ofmonohydrate feed which is being treated and on the amount of water vaporwhich must be removed during this treatment.

The exact reason for the agglomeration and solidification of the bariumhydroxide monohydrate particles after packaging or during storage is notknown. The following theory is offered to explain the bondingphenomenon, but it is to be understood that the invention is notintended to be bound to this explanation or theory of operation.

It is believed that the undesired agglomeration and solidification isdue to the presence of higher hydrates in the monohydrate product. Moreparticularly, it is believed that a substantial amount of higherhydrates, particularly the tetrahydrate, are present, along with themonohydrate. A product reported as having an assay of 97 percent byweight Ba(Ol-l) H O may contain as much as 4 to percent of higherhydrates because the water may be held in the form of higher hydrates.These higher hydrates have higher water vapor pressures than themonohydrate. As a result, the higher hydrates tend to try to distributetheir excess water to the monohydrate particles and in doing so themonohydrate flakes bond at their points of contact with one another onprolonged standing, as in packages or in storage.

By means of the present process, higher hydrates than the monohydrateare eliminated, and the resultant product is substantially free ofresidual water which can cause cementing and bonding of the monohydrateflakes at their points of contact with one another. As will be seen inthe foregoing examples, the increase in Ba(Ol-l) H O assay may be aslittle as 2 percent over conventional, commercial barium hydroxidemonohydrate products. However, this may be sufficient to eliminate from4 to l0 percent of the higher hydrates that commence the bonding andagglomeration of the remainder of the barium hydroxide monohydrateproduct. By removal of the higher hydrates, the barium hydroxidemonohydrate has been found to be free of any tendency to agglomerate orbond even after prolonged storage.

The following example is given to illustrate the invention but is notintended to limit the scope thereof in any way.

EXAMPLE 1 A concentrated, aqueous solution of barium hydroxide, having aconcentration of 62.3 percent by weight Ba(OH) was heated to 100 C. andfed into the bottom of a splash pan of a steam-heated, twin-surfaceddrier. The steam side temperature of the drier was maintained at 171 C.fl C. (340 F. 13 F.). The temperature of the outside surface of thedrier was maintained at about l2 l C. (250 F.). A splasher located inthe splash pan was run at about 400 r.p.m. to provide an even coating ofbarium hydroxide solution on the drier surface. The drying surfaces ofthedrier were rotated at 4 r.p.m. The product removed from the surfaceof the drier was dried flakes, which upon analysis of its bariumcontent, assayed 97.4% Ba(OH), H O (or 88.3% Ba(OH) The above bariumhydroxide monohydrate flakes were fed into a rotary kiln drier at a rateof about 30 pounds per square foot of heating area of the kilnper hour.The drier was heated by passing combustion gases around the outside ofthe kiln so that heat exchange was effected indirectly through the wallsof the drier. The temperature of the kiln was adjusted so that theproduct discharged from the kiln at a temperature of l20 C. Dry air,containing no morethan 0.03% C0,, was passed into the drier as the sweepgas at a rate of 10 cubic foot per minute per square foot of crosssectional area in the drier. The residence time of the flakes goingthrough the drier was about 8 minutes. The product removed from thedrier had the following analysis: v

99.6% by weight Ba(Ol-l), H O

The product was in the form of small flakes and had a bulk density of 60pounds per cubic foot and had the following size distribution: +8 meshl%, +60 mesh 62%, +200 mesh 76%, 200 mesh 24%.

Two Tote-Bin" containers were loaded with 4,500 pounds each of bariumhydroxide monohydrate. Tote-Bin" (A) was loaded with barium hydroxidemonohydrate produced as set forth above as it was recovered from thedrum drier without the post-drying treatment. Tote-Bin" (B) was loadedwith the product from the drier produced in accordance with the presentinvention. Both Tote-Bin containers were left for a period of 18 days.Once each day during this period the bins were placed on a reciprocatingplatform and subjected to pulsating, vertical displacements to simulaterailroad transport. This was carried out for 10 minutes a day.

At the end of the 18 days, the Tote-Bin containers were placed on aconventional bin vibrator used to shake up the bin to induce flow of theproduct during unloading. Tote-Bin" (A), containing the conventionalmonohydrate from a drum drier, had formed strong agglomerates and itscontents could not be discharged by the bin vibrators. The largeagglomerates had to be dislodged by banging the sides of the bin withcrowbars to break loose and dislodge the agglomerates in the container.Tote-Bin" (B), which contained the product of the rotary drier producedby the instant invention, discharged freely from the Tote-Bin" whenplaced on the conventional bin vibrator and yielded a free-flowingmonohydrate product.

Pursuant to the requirements of the Patent Statutes, the principle ofthis invention has been explained and exemplified in a manner so that itcan be readily practiced by those skilled in the art, suchexemplification including what is considered to represent the bestembodiment of the invention. However, it should be clearly understoodthat, within the scope of the appended claims, the invention may bepracticed by those skilled in the art, and having the benefit of thisdisclosure otherwise than as specifically described and exemplifiedherein.

What is claimed is:

1. In the process of producing barium hydroxide monohydrate wherein anaqueous solution of barium hydroxide containing from about 50 to about66 percent barium hydroxide is placed in a thin film on a heated surfaceand water is rapidly removed from said film to yield particlescontaining about 97 percent barium hydroxide monohydrate, theimprovement which comprises placing said particles in a heating zone andheating said particles to a temperature of from about l00 to C., passingan inert sweep gas over the 2. Process of claim 1 wherein saidfree-flowing particles of barium hydroxide monohydrate have a Ba(Ol-I) HO assay of at least about 99 percent.

3. Process of claim 1 wherein said sweep gas is dry air.

4. Process of claim 1 wherein said heating zone is a rotary kiln.

2. Process of claim 1 wherein said free-flowing particles of bariumhydroxide monohydrate have a Ba(OH)2 . H2O assay of at least about 99percent.
 3. Process of claim 1 wherein said sweep gas is dry air. 4.Process of claim 1 wherein said heating zone is a rotary kiln.